BIOLOGICAL VARIATIONS OF BACTERIA 391 



CHANGES IN MORPHOLOGY 



During the course of experimentation several of the strains 

 of B. coli showed a change in morphology, the individual organ- 

 isms becoming two and three times the length of those in the 

 controls, somewhat wider and more vacuolated. This however 

 was not constant, as often on the very next sub-culture they 

 would assume their usual morphological appearances. The only 

 other thing noted under this head was the decrease in motility, 

 which was more marked in the phenol broth than in the other 

 media. Very little importance should be attached to this, 

 however, since some of the strains were hardly motile to be- 

 gin with, and again, too few observations were made to permit 

 of absolute statements. 



GROWTH ON POTATO 



Glucose seemed to have a special effect upon the character 

 of growth of B. coli on this medium. Five of the seven treated 

 strains, showed at best only a very light yellow color or a slight 

 brownish growth on ordinary potato with practically no discolora- 

 tion of the medium. Very frequently indeed, the glucose affected 

 organisms would give the typical "invisible" growth seen with 

 the B. typhi. Both the original stock and the broth control 

 showed the characteristic colon growth on this medium. This 

 change was noted so many times that an explanation based on 

 differences in the composition of the potato can be excluded. 

 Three of these five strains also showed this change after exposure 

 to phenol. One strain of the B. coli, which did not change in 

 this respect with either glucose or phenol, showed this same 

 variation after growing in either sodium chloride or sodium 

 sulphate broth. 



ACTION IN MILK 



Both phenol and glucose diminished the acid production and 

 inhibited the formation of lab enzyme in three of the seven 

 strains of the B. coli, either entirely or for a period of at least 

 two weeks. These results were not seen with the use of the strong 

 saline or sodium sulphate broth. 



